The present invention relates to a valve control apparatus for generating an anticipatory output response for controlling a fluid flow in a fluid flow line and, more particularly, a valve control apparatus with a tunable anticipatory output response.
When changing a nuclear power plant configuration from a variable letdown/fixed charging chemical volume control system to a variable charging/fixed letdown control scheme, the letdown back-pressure controller is not able to control letdown back-pressure without employing the fluid flow line's relief system when a letdown orifice-type valve is opened under normal operating conditions. As the associated letdown orifice does not develop a pressure drop instantaneously, a transient pressure pulse passes through the letdown heat exchanger and associated piping to the letdown back-pressure valve because the response time associated with the instrumentation typically provided for a conventional proportional, integral, and derivative (PID) controller (approximately 300 ms plus valve response time at analog based, and 500 ms plus valve response time if microprocessor based) cannot change the output signal to the valve fast enough to overcome valve stiction and thereby control the transient pressure pulse without lifting the fluid flow line's relief.